Mobile communications systems, such as cellular or personal communications services (PCS) systems, are made up of a plurality of cells. Each cell provides a radio communications center in which a mobile unit establishes a call with another mobile unit or wireline unit connected to a public switched telephone network (PSTN). Each cell includes a radio base station, with each base station connected to a base station controller or mobile switching center that controls processing of calls between or among mobile units or mobile units and PSTN units.
Various wireless protocols exist for defining communications in a mobile network. One such protocol is a time-division multiple access (TDMA) protocol, such as the TIA/EIA-136 standard provided by the Telecommunications Industry Association (TIA). With TIA/EIA-136 TDMA, each channel carries a frame that is divided into six time slots to support multiple (3 or 6) mobile units per channel. Other TDMA-based systems include Global System for Mobile (GSM) communications systems, which use a TDMA frame divided into eight time slots (or burst periods).
Traditional speech-oriented wireless systems, such as the TIA/EIA-136 and GSM TDMA systems, utilize circuit-switched connection paths in which a line is occupied for the duration of the connection between a mobile unit and the mobile switching center. Such a connection is optimum for communications that are relatively continuous, such as speech. However, data networks such as local area networks (LANs), wide area networks (WANs), and the Internet use packet-switched connections, in which communication between nodes on a communications link is by data packets. Each node occupies the communications link only for as long as the node needs to send or receive data packets. With the rapid increase in the number of cellular subscribers in conjunction with the rising popularity of communications over data networks such as intranets or the Internet, a packet-switched wireless data connection that provides convenient and efficient access to data networks, electronic mail, databases, and other types of data has become desirable.
Several packet-switched wireless connection protocols have been proposed to provide more efficient connections between a mobile unit and a data network. One such protocol is the General Packet Radio Service (GPRS) protocol, which complements existing GSM systems. Another technology that builds upon GPRS is the Enhanced Data Rate for Global Evolution (EDGE) technology, which offers even higher data rates. The enhancement of GPRS by EDGE is referred to as Enhanced GPRS (EGPRS). Another variation of EGPRS is the EGPRS COMPACT technology.
The packet-switched wireless connection protocols provide efficient access to traditional data networks, such as the Internet, LANs, WANs, and the like. A growing use of such data networks is for voice and other forms of real-time or streaming communications (such as video, audio and video, and so forth). Various protocols have been defined to enable such real-time or streaming communications over the data networks, which are often packet-switched networks. A popular packet-switched network is the Internet Protocol (IP) network.
To establish calls over IP networks, Session Initiation Protocol (SIP), H.323, or other types of messages can be used. Once a call is established, other communications protocols are used to provide for reliable real-time communications. Such other protocols include the Real-Time Protocol (RTP), Resource Reservation Protocol (RSVP), and others. However, with the relatively large size of typical messages, such as SIP, RSVP, or H.323 messages, unacceptably large delays may be introduced when attempting to establish a packet-based call session over a wireless network.
As wireless networks continue to evolve, a need exists for improved methods and mechanisms to enable voice and other forms of real-time or streaming communications over packet-switched wireless networks.